I know from experience that it's best to extract the oil with one needle, then change to a new one to inject for a less painful experience, as the syringe gets a little dulled going through the rubber stopper. Is it SAFE and SANITARY if I extract with a needle, unscrew it off, and LEAVE THAT NEEDLE STICKING OUT OF THE 10 ML VIAL, so I can continuously just unscrew a new syringe and screw it on to the needle sticking out of the vial, draw up the oil, unscrew, then screw it back on to the original/new needle it was on??? Do you guys get what I'm saying? I just don't have enough syringes on hand to ALWAYS use two needles. What do you think???